<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>输入年龄显示季节</title>
</head>
<body>
    
</body>
<script>
    var season = prompt('输入年份显示季节')
    if (season == null) {
        alert('请输入月份')
    } else if (season <= 3) {
        alert('春季')
    } else if (season <= 6) {
        alert('夏季')
    } else if (season <= 9) {
        alert('秋季')
    } else if (season <= 12) {
        alert('冬季')
    } else {
        alert('没有此月份')
    }
</script>
</html>